This invention relates to a rotary atomizing head type coating machine which is suitable for use, for example, for coating vehicle bodies or the like.
Generally, rotary atomizing head type coating machines have been widely resorted to for coating vehicle bodies or similar work pieces. Shown by way of example in FIGS. 16 and 17 is a prior art rotary atomizing head type coating machine of this sort.
In these figures, indicated at 100 is a rotary atomizing head type coating machine as a whole. The rotary atomizing head type coating machine 100 is largely constituted by a machine cover 101 which is formed in a tubular shape, an air motor 102 which is accommodated in the cover machine 101, a rotational shaft 103 which is passed axially through the air motor 102 and rotationally driven by the latter, and a rotary atomizing head 104 which is mounted on the rotational shaft 103 on the front side of the machine cover 101 and thereby rotated at a high speed, for example, at a speed of 3,000 to 100,000 rpm to atomize and spray paint.
More specifically, as shown in FIG. 17, the rotational shaft 103 is provided with a male screw portion 103A around the circumference of a front end portion which is projected forward of the air motor 102. The rear side of the rotary atomizing head 104 is formed into a rotational shaft mount portion 104A of a tubular shape to receive therein a fore end portion of the rotational shaft 103. The rotational shaft mount portion 104A is provided with a female screw portion 104B on a deep inner peripheral portion for threaded engagement with the male screw portion 103A of the rotational shaft 103. The rotational shaft 103 and the rotary atomizing head 104 are integrally fixed to each other by tightly threading the male screw portion 103A into the female screw portion 104B.
A feed tube 105 is passed through the rotational shaft 103, and the fore end of the feed tube 105 is projected from the rotational shaft 103 and extended into the rotary atomizing head 104. A paint passage 105A and a thinner passage 105B are provided internally of the feed tube 105.
Further, an annular shaping air ring 106 is detachably attached to the front side of the machine cover 101, on the outer peripheral side of the rotary atomizing head 104. In order to control the spray pattern of paint which is sprayed by the rotary atomizing head 104, a large number of air outlet holes 106A are formed in this shaping air ring 106 at intervals in a circumferential direction for spurting shaping air toward sprayed paint particles.
In the case of the rotary atomizing head type coating machine 100 which is constructed in the manner as described above, while the rotary atomizing head 104 is put in high speed rotation by the air motor 102, paint is supplied to the rotary atomizing head 104 through the feed tube 105. Since the rotary atomizing head 104 is in high speed rotation, the supplied paint is atomized into fine particles under the influence of centrifugal force and sprayed forward. The spray pattern of paint particles is controlled by shaping air which is spurted from the shaping air ring 106 while paint particles are sprayed forward for deposition on a work piece.
By the way, according to the above-described prior art rotary atomizing head type coating machine 100, the rotational shaft 103 and the rotary atomizing head 104 are fixed to each other by threaded engagement of the male and female screw portions 103A and 104B. The screw threads of these screw portions 103A and 104B are tapped in the opposite direction with respect to the direction of rotation of the rotary atomizing head 103, more specifically, are tapped as right-turn screws in a case where the rotary atomizing head 103 is put in rotation in a counterclockwise direction as seen arrow a in FIG. 16 (turning leftward when seen from the front side of the rotary atomizing head 104). Therefore, when the rotational speed of the air motor 102 is on the increase, the rotational shaft 103 is tightened relative to the rotary atomizing head 104. On the other hand, when the rotational speed of the air motor 102 is on the decrease, the rotational shaft 103 is loosened relative to the atomizing head 104.
Nevertheless, should a trouble occur to a drive portion of the air motor 102 when it is in high speed rotation, the rotational speed of the air motor 102 could drop abruptly and the rotation itself could be totally stopped. Besides, for the purpose of changing the paint feed rate to the rotary atomizing head 104 or for the purpose of washing the rotary atomizing head 104 prior to a color change, there may often arise a necessity for dropping the rotational speed of the air motor 102 abruptly from about 30,000 rpm to about 10,000 rpm.
In such a case, despite an abrupt drop in rotational speed of the rotational shaft 103, the rotary atomizing head 104 tends to maintain a current rotational speed under the influence of inertial force, as a result acting to loosen the screw portions 103A and 104A, that is to say, to loosen the rotary atomizing head 104 relative to the rotational shaft 103. Therefore, while the air motor 102 is in high speed rotation, an abrupt drop of the air motor speed can lead to loosening and fall-off of the rotary atomizing head 104 from the rotational shaft 103.
Further, the rotary atomizing head 104 is subjected to large centrifugal force while in high speed rotation, and as a result the atomizing head mount portion 104A is spread in radially outward directions, lowering the gripping force of the male and female screw portions 103A and 104B of the rotational shaft 103 and the rotary atomizing head 104. Thus, upon a conspicuous drop in operating speed of the rotational shaft 103 or a sudden stop of the rotational shaft 103, the male and female screw portions 103A and 104B can be loosened until the rotary atomizing head 104 falls off the rotational shaft 103.
If the rotary atomizing head 104 should fall off the rotational shaft 103 during high speed rotation, it would be thrown away and hit against nearby equipments and work pieces, resulting in serious damages not only to the rotary atomizing head 104 itself but also to the nearby equipments and work pieces.
On the other hand, according to another prior art rotary atomizing head type coating machine, an O-ring is fitted on the outer periphery of a fore end portion of the rotational shaft or in the inner periphery of the rotary atomizing head mount portion to mount the rotary atomizing head on the rotational shaft through resilient force of the O-ring (e.g., as disclosed in Japanese Patent Laid-Open No. H11-28391).
However, in the case of the another prior art just mentioned, there is a problem of abrasive damages to the O-ring because the surface of the O-ring is abraded every time the rotary atomizing head is mounted on or dismantled from the rotational shaft. If an O-ring is used in a damaged state, it may no longer be able to stop the rotary atomizing head from falling off the rotational shaft because its force of fixing the rotary atomizing head to the rotational shaft is weakened considerably in the abrasive damage.
In view of the above-discussed problems with the prior art, it is an object of the present invention to provide a rotary atomizing head type coating machine which is, for the sake of higher reliability of operation and higher productivity, so arranged as to prevent a rotary atomizing head from coming off or from being thrown away from a rotational shaft when it is loosened relative to the latter while in operation.
The present invention is directed to a rotary atomizing head type coating machine of the sort which includes a high speed rotational drive source, a rotational shaft rotatably supported at a base end thereof by the rotational drive source and having a fore end portion projected on the front side of the rotational drive source, a rotary atomizing head having on the front side thereof a paint atomizing portion for atomizing supplied paint into finely divided particles and on the rear side a tubular mount portion to be mounted on a projected fore end portion of the rotational shaft, and a shaping air spurting means having an inner peripheral side thereof located in such a way as to circumvent outer periphery of the rotary atomizing head and adapted to spurt shaping air toward paint particles sprayed by the rotary atomizing head.
According to the present invention, for solving the above-discussed problems, there is provided a rotary atomizing head type coating machine which is characterized by the provision of: an outward projection provided on and projected radially outward from a circumferential surface of the tubular mount portion of the rotary atomizing head; and an inward projection provided on and projected radially inward from an inner peripheral surface of the shaping air spurting means and adapted to be brought into abutting engagement with the outward projection when the rotary atomizing head is loosened relative to the rotational shaft to prevent the rotary atomizing head from falling off the rotational shaft.
With the arrangements just described, in case the rotary atomizing head is loosened relative to the rotational shaft while in rotation and its position is shifted in axial direction, the outward projection which is projected radially outward from a circumferential surface of the tubular mount portion of the rotary atomizing head is abutted against the inward projection which is projected radially inward from an inner peripheral surface of a shaping air ring, thereby preventing the rotary atomizing head from falling off or from being thrown away from the rotational shaft in a completely freed state.
According to a preferred form of the present invention, the rotational shaft is provided with a male screw portion on a fore end portion thereof while the rotary atomizing head is provided with a female screw portion within the tubular mount portion for threaded engagement with the male screw portion, and the outward and inward projections are adapted to be brought into abutting engagement with each other when position of the rotary atomizing head is shifted in a forward direction relative to the rotational shaft as a result of loosening of a threaded joint of the male and female screw portions.
With the arrangements just described, when the threaded joint portion of the male and female screws is loosened, for example, by an abrupt drop in rotational speed of the rotational shaft and the position of the loosened rotary atomizing head is shifted in an axially forward direction relative to the rotational shaft, the outward projection is abutted against the inward projection thereby to prevent the rotary atomizing head from coming off the rotational shaft in a freed state.
According to another preferred form of the present invention, the outward projection is positioned axially on the rear side of the inward projection when the rotary atomizing head is mounted in position on a fore end portion of the rotational shaft.
According to still another preferred form of the present invention, the shaping air spurting means is provided with a fore inner peripheral surface portion for accommodating the paint atomizing portion and a rear inner peripheral surface portion for accommodating the tubular mount portion of the rotary atomizing head, and the inward projection is provided in a boundary inner peripheral surface between the fore and rear inner peripheral surface portions.
According to a further preferred form of the present invention, the outward projection is provided at a plural number of positions on the circumference of the tubular mount portion of the rotary atomizing head at intervals in rotational direction, and the inward projection is provided at a plural number of positions on the inner periphery of the shaping air ring at intervals in rotational direction correspondingly to the outward projection in such a way as to define therebetween an outward projection passageway which permits passage of the outward projections only when the latter are in a conforming angular position.
With the arrangements just described, at the time of mounting or dismantling the rotary atomizing head on or from the rotational shaft, the outward projections on the side of the rotary atomizing head are turned into a conforming angular position relative to the outward projection passageway between the inward projections on the side of the shaping air spurting means, and in this state the tubular mount portion of the rotary atomizing head is advanced straightforward into the shaping air spurting means, letting the outward projections pass adjacent inward projections on the side of the shaping air spurting means. After passing the inward projections in this way, the rotary atomizing head can be mounted on or dismantled from the rotational shaft.
On the other hand, while the rotational shaft and the rotary atomizing head are in rotation, the outward projections are also put in rotation. Therefore, in the event the rotary atomizing head is loosened relative to the rotational shaft while in rotation, it is almost impossible for the plural number of outward projections, which are also in rotation, to pass through the outward projection passageway. Instead, the outward projections are abutted against the inward projections to prevent the rotary atomizing head from coming or falling off the rotational shaft.
According to a further preferred form of the present invention, the outward projection is constituted by a plural number of segmental outward projections projected radially outward at radially opposite positions on the circumference of the tubular mount portion of the rotary atomizing head and having truncated side portions at opposite sides thereof, and the inward projection is constituted by a plural number of D-shaped inward projections provided at radially opposite positions on the inner periphery of the shaping air spurting means in such a way as to form therebetween an outward projection passageway which permits passage of the outward projections only when the latter are in a conforming angular position.
With the arrangements just described, at the time of mounting or dismantling the rotary atomizing head on or from the rotational shaft, the segmental outward projections on the side of the rotary atomizing head are turned into a conforming angular position relative to the outward projection passageway on the side of the shaping air spurting means, with the truncated sides of the segmental outward projections in parallel relation with inner ends of the D-shaped inward projections. In this state, the tubular mount portion of the rotary atomizing head is advanced straightforward into the shaping air spurting means, letting the segmental outward projections pass through the outward projection passageway. After passing the inward projections in this way, the rotary atomizing head can be mounted on or dismantled from the rotational shaft.
On the other hand, while the rotational shaft and the rotary atomizing head are in rotation, the segmental outward projections are also put in rotation. Therefore, in the event the rotary atomizing head is loosened relative to the rotational shaft while in rotation, it is almost impossible for the segmental outward projections, which are also in rotation, to pass through the outward projection passageway. Instead, the segmental outward projections are abutted against the D-shaped inward projections.
According to a further preferred form of the present invention, at least either the outward projection or the inward projections is provided at a plural number of positions which are shifted in axial and rotational directions.
With the arrangements just described, in case an outward projection at one position should pass an adjacent inward projection although it is extremely improbable, other outward and inward projections are abutted against each other to prevent the rotary atomizing head from coming off the rotational shaft in a double assured manner.
According to a further preferred form of the present invention, the shaping air spurting means is detachably attached on the side of the rotational shaft, the outward projection is constituted by an annular outward projection formed around the entire circumference of the tubular mount portion of the rotary atomizing head, and the inward projection on the side of the shaping air spurting means is formed in an inside diameter larger than an outside diameter of the paint atomizing portion of the rotary atomizing head, the shaping air spurting means being removable from the machine before mounting or dismantling the rotary atomizing head on or from the rotational shaft.
With the arrangements just described, at the time of assembling the rotary atomizing head, firstly the rotary atomizing head is mounted on the rotational shaft and then the shaping air spurting means is attached to the machine in such a way as to circumvent the outer periphery of the rotary atomizing head, letting the inward projection pass over and along the outer periphery of the rotary atomizing head. In the event the rotary atomizing head is loosened relative to the rotational shaft, the annular outward projection is abutted against the inward projection on the side of the shaping air spurting means thereby to prevent the rotary atomizing head from falling off or from being thrown away from the rotational shaft.
On the other hand, at the time of disassembling the rotary atomizing head, the shaping air spurting means can be removed by passing the inward projection over and along the outer periphery of the paint atomizing portion of the rotary atomizing head, before dismantling the rotary atomizing head from the rotational shaft.
According to the present invention, there is also provided a rotary atomizing head type coating machine of the sort as mentioned above, which is characterized by the provision of: an annular outward projection formed around and projected radially outward from entire circumference of the tubular mount portion of the rotary atomizing head; a stopper anchor hole formed into the shaping air spurting means across and inward of an inner peripheral surface of the latter; and a stopper member fitted in the stopper anchor hole and adapted to be brought into abutting engagement with the annular outward projection when the rotary atomizing head is loosened relative to the rotational shaft to prevent the rotary atomizing head from falling off the rotational shaft.
With the arrangements just described, at the time of mounting or dismantling the rotary atomizing head on or from the rotational shaft, the stopper member is removed from the stopper anchor hole in the shaping air spurting means. Upon removal of the stopper member, the rotary atomizing head can be mounted on or dismantled from the rotational shaft. After connecting the rotary atomizing head to the rotational shaft, the stopper member is fitted in the stopper anchor hole. When set in position, the stopper member which is passed radially inward of the inner periphery of the shaping air spurting means is partly projected to form an inward projection on the inner periphery of the shaping air spurting means. Therefore, when the rotary atomizing head is loosened relative to the rotational shaft, the annular outward projection on the side of the rotary atomizing head is brought into abutting engagement with the stopper member to prevent the rotary atomizing head from coming off or from being thrown away from the rotational shaft.
According to a further preferred form of the present invention, the stopper anchor hole is positioned axially on the front side of the annular outward projection when the rotary atomizing head is mounted in position on the rotational shaft.
Accordingly to the present invention, preferably a machine cover is provided on the machine in such a way as to circumvent outer periphery of the rotational drive source, and the shaping air spurting means is attached to a front end portion of the machine cover.